Nanomotors shake up living cells from the inside

Chemists and engineers at Penn State University have placed synthetic motors inside live human cells, propelled them with ultrasonic waves and steered them magnetically.

The nanomotors, which are rocket-shaped metal particles, move around inside the cells, spinning and knocking against the cell membrane. Applications are foreseen in medicine.

‘As these nanomotors move around and bump into structures inside the cells, the live cells show internal mechanical responses that no one has seen before,’ said Tom Mallouk, Evan Pugh Professor of Materials Chemistry and Physics at Penn State. ‘We might be able to use nanomotors to treat cancer and other diseases by mechanically manipulating cells from the inside. Nanomotors could perform intracellular surgery and deliver drugs non-invasively to living tissues.’

Chemically powered nanomotors first were developed ten years ago at Penn State by a team that included chemist Ayusman Sen and physicist Vincent Crespi, in addition to Mallouk.

‘Our first-generation motors required toxic fuels and they would not move in biological fluid, so we couldn’t study them in human cells,’ Mallouk said in a statement.

When Mallouk and French physicist Mauricio Hoyos discovered that nanomotors could be powered by ultrasonic waves, the door was open to studying the motors in living systems.

For their experiments, the team used HeLa cells, a line of human cervical cancer cells often used in research studies. These cells ingest the nanomotors, which then move around within the cell tissue, powered by ultrasonic waves.

At low ultrasonic power the nanomotors have little effect on the cells but when the power is increased, the nanomotors become more active, moving around and bumping into organelles, which are structures within a cell that perform specific functions. Magnetic forces can then be applied to control the motors further by steering them.

Mallouk and his colleagues also found that the nanomotors can move autonomously, an ability that is important for future applications.

‘Autonomous motion might help nanomotors selectively destroy the cells that engulf them,’ Mallouk said. ‘If you want these motors to seek out and destroy cancer cells, for example, it’s better to have them move independently. You don’t want a whole mass of them going in one direction.’

The ability of nanomotors to affect living cells holds promise for medicine, Mallouk said. ‘One dream application of ours is…where nanomotors would cruise around inside the body, communicating with each other and performing various kinds of diagnoses and therapy. There are lots of applications for controlling particles on this small scale, and understanding how it works is what’s driving us.’

The researchers’ findings have been published in Angewandte Chemie International Edition. Co-authors include Penn State researchers Wei Wang, Sixing Li, Suzanne Ahmed, and Tony Jun Huang, as well as Lamar Mair of Weinberg Medical Physics in Maryland.

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